This invention relates to a heat activated heat pump and particularly to a free piston version of so-called Vulleumier heat pump.
A type of conventional Vulleumier heat pump is disclosed in U.S. Pat. No. 1,275,507. This conventional heat pump has a pair of cylinders disposed opposite to each other in which a pair of displacers are so accommodated as to be moved with a certain time lag between the two displacers. Working gas in the two cylinders is moved reciprocally among hot, cold and intermediate chambers through a heater, regenerator and a cooler. In this known heat pump, the two displacers are displaced by a driving shaft disposed between the two displacers via a crank mechanism.
Further, U.S. Pat. No. 3,630,041 discloses a heat pump in which two displacers are moved by two separated driving motors. In addition, U.S. Pat. No. 3,774,405 discloses a heat pump in which two permanent magnets are provided on two displacers, respectively, so that the displacers can be moved by their magnetic force. U.S. Pat. No. 3,379,026 discloses a type of heat pump in which two displacers are moved reciprocally by a force of working gas and the reciprocal movement of the displacers is transferred into a rotational movement via a crank mechanism so that a rotational force is taken out as a driving force for an external mechanical apparatus. Moreover, a conventional heat pump in which an intermediate chamber is partitioned by a floating piston is disclosed in U.S. Pat. No. 4,455,841. In addition to these conventional heat pumps, U.S. Pat. No. 4,024,727 discloses a heat pump in which a cold displacer functions as a free piston and is supported by a gas spring so that the cold displacer is moved due to a difference in area receiving pressure of working gas.
In these conventional heat pumps, crank mechanisms are provided therein and at least one displacer is moved by an outer mechanical force or a magnetic force. Therefore, the construction of each heat pump becomes complexed and each heat pump cannot be operated without an outer driving source.